Aerodynamic considerations for a speed plane design
03-30-2008 | 11:20 AM
#1
Thread Starter
Aerodynamic considerations for a speed plane design
I want to start a thread about the aerodynamic considerations of speed plane designs.
It is my understanding that in pylon racing there are many limitations as to what you can do, we are going to ignore those limitations here.
This thread will focus on building an aircraft for the fastest time through the traps.
It is my understanding that in pylon racing there are many limitations as to what you can do, we are going to ignore those limitations here.
This thread will focus on building an aircraft for the fastest time through the traps.
03-30-2008 | 11:50 AM
#3
Thread Starter
RE: Aerodynamic considerations for a speed plane design
Well as far as powered airplanes we have several choices...
Perhaps we should break it down to IC engines, electric, or turbines.
But for the moment lets just focus on the basics of airframe, airfoil, control and drag reduction. Then we can tailor the airfame to match the power setup.
So a look at the record holder even if it is not powered would be important.
Perhaps we should break it down to IC engines, electric, or turbines.
But for the moment lets just focus on the basics of airframe, airfoil, control and drag reduction. Then we can tailor the airfame to match the power setup.
So a look at the record holder even if it is not powered would be important.
03-30-2008 | 01:34 PM
#5
Thread Starter
RE: Aerodynamic considerations for a speed plane design
What I found was your basic sailplane or slope soarer, low drag design.
So I guess for the purpose of this thread lets work on the premise that we are looking at a powered airplane.
So I guess for the purpose of this thread lets work on the premise that we are looking at a powered airplane.
03-30-2008 | 01:44 PM
#6
My Feedback: (60)
RE: Aerodynamic considerations for a speed plane design
Well, according to your first post, you are taking Turbines out of the race because you indicate "Through the speed traps". Unless of course you are going to attempt this somewhere that the AMA is not involved. AMA rules indicate that turbine powered fixed wing aircraft shall not be flown through speed traps.
03-30-2008 | 02:10 PM
#7
Thread Starter
RE: Aerodynamic considerations for a speed plane design
Perhaps then some other method to determine the speed of the aircraft has to be used...
Although I feel that it is a given that turbine powered aircraft would best suited for absolute speed, perhaps we should not use them as a method of power in this discussion.
What I want to focus on is the aerodynamic consideration of high speed designs, the power source is secondary to the primary consideration at this point.
So lets just look at what makes a speed plane, a speed plane.
Although I feel that it is a given that turbine powered aircraft would best suited for absolute speed, perhaps we should not use them as a method of power in this discussion.
What I want to focus on is the aerodynamic consideration of high speed designs, the power source is secondary to the primary consideration at this point.
So lets just look at what makes a speed plane, a speed plane.
03-30-2008 | 02:16 PM
#8
RE: Aerodynamic considerations for a speed plane design
ORIGINAL: iron eagel
Perhaps then some other method to determine the speed of the aircraft has to be used...
Although I feel that it is a given that turbine powered aircraft would best suited for absolute speed, perhaps we should not use them as a method of power in this discussion.
What I want to focus on is the aerodynamic consideration of high speed designs, the power source is secondary to the primary consideration at this point.
So lets just look at what makes a speed plane, a speed plane.
Perhaps then some other method to determine the speed of the aircraft has to be used...
Although I feel that it is a given that turbine powered aircraft would best suited for absolute speed, perhaps we should not use them as a method of power in this discussion.
What I want to focus on is the aerodynamic consideration of high speed designs, the power source is secondary to the primary consideration at this point.
So lets just look at what makes a speed plane, a speed plane.
better get your parameters figuredout
a very draggy looking setup with enough power may proove to be the fastest
consider a rocket powered model------
The slope setup which uses momma nature is easily the best scxample of drag reduction and maximization of lifting area.
Are you after an infernal powered setup- ?
what?
03-30-2008 | 02:19 PM
#9
RE: Aerodynamic considerations for a speed plane design
Since this is the aerodynamics forum and IE has said let's go for broke and DARN to the rules we can toss out the AMA restriction on turbines for whatever reason they put it into place. To a great extent a lot of this will be theoretical in any event.
There's no doubt that the power source is 95% of the equation on a speed model. The Extreme Speed Prop forum is full of models that fly very fast but do not have the best aerodynamics by any means. Brute power is obviously the cornerstone. But given two identical brute power sources what is needed to make one go a lot faster than the other? Now we come down to cleaning up the airframe so that the engine can spin a higher pitch prop and still unload enough to get up to the peak HP figure. And THAT is going to get us the extra speed.
There's no doubt that the power source is 95% of the equation on a speed model. The Extreme Speed Prop forum is full of models that fly very fast but do not have the best aerodynamics by any means. Brute power is obviously the cornerstone. But given two identical brute power sources what is needed to make one go a lot faster than the other? Now we come down to cleaning up the airframe so that the engine can spin a higher pitch prop and still unload enough to get up to the peak HP figure. And THAT is going to get us the extra speed.
03-30-2008 | 03:23 PM
#10
Thread Starter
RE: Aerodynamic considerations for a speed plane design
By Bm
"There's no doubt that the power source is 95% of the equation on a speed model. The Extreme Speed Prop forum is full of models that fly very fast but do not have the best aerodynamics by any means. Brute power is obviously the cornerstone. But given two identical brute power sources what is needed to make one go a lot faster than the other? Now we come down to cleaning up the airframe so that the engine can spin a higher pitch prop and still unload enough to get up to the peak HP figure. And THAT is going to get us the extra speed."
That is what I was thinking...
Now given that most of us do not have access to the funds needed for turbines, my self included.
How do we take a glow/gas/electric powered airplane with a prop to the next level.
Some of the restrictions placed on pylon racers such as non tapered wings no fillets place severe limits on cleaning up the airframe.
I think that there some questions about different wing designs used for speed. In modern aircraft the swept wings and deltas of the 50's and 60's have been replaced by short stubby wings, at least for modern fighters. And concepts such as BWB are just now being explored in commercial and GA aircraft.
One would think that the BWB concept would lend itself to higher speeds where it could be setup to produce far less drag than the typical tube and wing designs now in use.
Another thought is regarding canards they seem to perfect for high speed flight but have never been mentioned as a possibility.
What I want is theoretical discussion on the subject, that perhaps some or all could be applied to building a aircraft that could exceed the present limitations, or allow someone to build a plane that may be a bit faster.
edit to add:
One comment in another thread regarding speed planes made by CP was, "Most of your speed plane designs look like model locomotives with wings". And they do indeed look much like the streamlined locomotives of the late 40's and 50's there has got to be a better way to build them...
"There's no doubt that the power source is 95% of the equation on a speed model. The Extreme Speed Prop forum is full of models that fly very fast but do not have the best aerodynamics by any means. Brute power is obviously the cornerstone. But given two identical brute power sources what is needed to make one go a lot faster than the other? Now we come down to cleaning up the airframe so that the engine can spin a higher pitch prop and still unload enough to get up to the peak HP figure. And THAT is going to get us the extra speed."
That is what I was thinking...
Now given that most of us do not have access to the funds needed for turbines, my self included.
How do we take a glow/gas/electric powered airplane with a prop to the next level.
Some of the restrictions placed on pylon racers such as non tapered wings no fillets place severe limits on cleaning up the airframe.
I think that there some questions about different wing designs used for speed. In modern aircraft the swept wings and deltas of the 50's and 60's have been replaced by short stubby wings, at least for modern fighters. And concepts such as BWB are just now being explored in commercial and GA aircraft.
One would think that the BWB concept would lend itself to higher speeds where it could be setup to produce far less drag than the typical tube and wing designs now in use.
Another thought is regarding canards they seem to perfect for high speed flight but have never been mentioned as a possibility.
What I want is theoretical discussion on the subject, that perhaps some or all could be applied to building a aircraft that could exceed the present limitations, or allow someone to build a plane that may be a bit faster.
edit to add:
One comment in another thread regarding speed planes made by CP was, "Most of your speed plane designs look like model locomotives with wings". And they do indeed look much like the streamlined locomotives of the late 40's and 50's there has got to be a better way to build them...
03-30-2008 | 04:01 PM
#11
RE: Aerodynamic considerations for a speed plane design
ORIGINAL: iron eagel
By Bm
"There's no doubt that the power source is 95% of the equation on a speed model. The Extreme Speed Prop forum is full of models that fly very fast but do not have the best aerodynamics by any means. Brute power is obviously the cornerstone. But given two identical brute power sources what is needed to make one go a lot faster than the other? Now we come down to cleaning up the airframe so that the engine can spin a higher pitch prop and still unload enough to get up to the peak HP figure. And THAT is going to get us the extra speed."
That is what I was thinking...
Now given that most of us do not have access to the funds needed for turbines, my self included.
How do we take a glow/gas/electric powered airplane with a prop to the next level.
Some of the restrictions placed on pylon racers such as non tapered wings no fillets place severe limits on cleaning up the airframe.
I think that there some questions about different wing designs used for speed. In modern aircraft the swept wings and deltas of the 50's and 60's have been replaced by short stubby wings, at least for modern fighters. And concepts such as BWB are just now being explored in commercial and GA aircraft.
One would think that the BWB concept would lend itself to higher speeds where it could be setup to produce far less drag than the typical tube and wing designs now in use.
Another thought is regarding canards they seem to perfect for high speed flight but have never been mentioned as a possibility.
What I want is theoretical discussion on the subject, that perhaps some or all could be applied to building a aircraft that could exceed the present limitations, or allow someone to build a plane that may be a bit faster.
edit to add:
One comment in another thread regarding speed planes made by CP was, "Most of your speed plane designs look like model locomotives with wings". And they do indeed look much like the streamlined locomotives of the late 40's and 50's there has got to be a better way to build them...
By Bm
"There's no doubt that the power source is 95% of the equation on a speed model. The Extreme Speed Prop forum is full of models that fly very fast but do not have the best aerodynamics by any means. Brute power is obviously the cornerstone. But given two identical brute power sources what is needed to make one go a lot faster than the other? Now we come down to cleaning up the airframe so that the engine can spin a higher pitch prop and still unload enough to get up to the peak HP figure. And THAT is going to get us the extra speed."
That is what I was thinking...
Now given that most of us do not have access to the funds needed for turbines, my self included.
How do we take a glow/gas/electric powered airplane with a prop to the next level.
Some of the restrictions placed on pylon racers such as non tapered wings no fillets place severe limits on cleaning up the airframe.
I think that there some questions about different wing designs used for speed. In modern aircraft the swept wings and deltas of the 50's and 60's have been replaced by short stubby wings, at least for modern fighters. And concepts such as BWB are just now being explored in commercial and GA aircraft.
One would think that the BWB concept would lend itself to higher speeds where it could be setup to produce far less drag than the typical tube and wing designs now in use.
Another thought is regarding canards they seem to perfect for high speed flight but have never been mentioned as a possibility.
What I want is theoretical discussion on the subject, that perhaps some or all could be applied to building a aircraft that could exceed the present limitations, or allow someone to build a plane that may be a bit faster.
edit to add:
One comment in another thread regarding speed planes made by CP was, "Most of your speed plane designs look like model locomotives with wings". And they do indeed look much like the streamlined locomotives of the late 40's and 50's there has got to be a better way to build them...
a lot of streamlining may look pleasing but the smallest lightest one will do the most with a given amount of power.
Canards?
ferget it
build somethinglike a class A control line speed plane with aileron and elevator control - as a starting point.
03-30-2008 | 04:13 PM
#12
Thread Starter
RE: Aerodynamic considerations for a speed plane design
Dick,
What about BWB?
As far as a canard, I was thinking along the lines of a twin wing mounted tractor setup, rather than the typical pusher setup. Round fuselage blended into the main wing, engines enclosed within wing mounted nacelles. The rudders also would be mounted on the wing as part of the nacelles. But that is going to be a interesting build in and of itself regardless of the speed it flies.
What about BWB?
As far as a canard, I was thinking along the lines of a twin wing mounted tractor setup, rather than the typical pusher setup. Round fuselage blended into the main wing, engines enclosed within wing mounted nacelles. The rudders also would be mounted on the wing as part of the nacelles. But that is going to be a interesting build in and of itself regardless of the speed it flies.
03-30-2008 | 04:29 PM
#13
Senior Member
My Feedback: (3)
RE: Aerodynamic considerations for a speed plane design
A Captain in the US Airforce and his jump suit has that DS models' speed covered. I hear that by the time he landed, he had his orders for Major.
What did this DS model clock through an entire 1/8th mile level timing zone, after first flying through a 1/8th mile long leveling off zone?
I think the parameters are very important to establish first. The rules that are already in place at the European Speed Cup have been developed after many years of weeding out what the event should represent. They have set max wingloadings and I believe a 10cc limit. The planes are overpropped gliders that need to be dived to get the powerplant on step, then the timing zone is a very shallow slope that is about 200 meters IIRC. The planes enter the zone at 50 feet and exit at 15 feet ideally. I don't know if this is the FAI standard or not.
High Plains has extrapolated what the theoretic HP needs to be for these planes to do what they do.....the figure was pretty high. An equivolent wattage could be used for an electric plane discussion here.
One thing that High Plains has mentioned recently is that full length fairings probably have more drag than just a short wind screen for rear exhaust models. I'm all for that idea!
What did this DS model clock through an entire 1/8th mile level timing zone, after first flying through a 1/8th mile long leveling off zone?
I think the parameters are very important to establish first. The rules that are already in place at the European Speed Cup have been developed after many years of weeding out what the event should represent. They have set max wingloadings and I believe a 10cc limit. The planes are overpropped gliders that need to be dived to get the powerplant on step, then the timing zone is a very shallow slope that is about 200 meters IIRC. The planes enter the zone at 50 feet and exit at 15 feet ideally. I don't know if this is the FAI standard or not.
High Plains has extrapolated what the theoretic HP needs to be for these planes to do what they do.....the figure was pretty high. An equivolent wattage could be used for an electric plane discussion here.
One thing that High Plains has mentioned recently is that full length fairings probably have more drag than just a short wind screen for rear exhaust models. I'm all for that idea!
03-30-2008 | 07:35 PM
#14
Thread Starter
RE: Aerodynamic considerations for a speed plane design
Well I guess the first thing to drop would be the 10 cc limit...
Lets say for a starting point we set 1.6 cu inches as a max displacement, or any combination of engines for that max. So we can look at building an airplane rather than an overpropped glider.
Lets try to set a few parameters, wing loading should be up to the builder, but for a max model weight lets say half of the AMA legal limit or 27.5 lbs dry, on a 8 foot max span wing. How does that sound?
Lets try to come up with something that can push the limits of R/C speed but be within the reach of the average hobby budget. If you have a better idea of what design should be used as a starting point then by all means join in. Keeping in mind this goes more toward an unlimited class than an FAI type of aircraft.
Lets say for a starting point we set 1.6 cu inches as a max displacement, or any combination of engines for that max. So we can look at building an airplane rather than an overpropped glider.
Lets try to set a few parameters, wing loading should be up to the builder, but for a max model weight lets say half of the AMA legal limit or 27.5 lbs dry, on a 8 foot max span wing. How does that sound?
Lets try to come up with something that can push the limits of R/C speed but be within the reach of the average hobby budget. If you have a better idea of what design should be used as a starting point then by all means join in. Keeping in mind this goes more toward an unlimited class than an FAI type of aircraft.
03-30-2008 | 09:15 PM
#15
My Feedback: (1)
RE: Aerodynamic considerations for a speed plane design
I'd stay at 15 cc or less or perhaps the big BVM .96 (made by Nelson). You need an engine that turns rpm so the props are closer to square.
The other thing, for maximum engine performance, make it a side mounted engine. I will leave it to you guys to figure out why.
The other thing, for maximum engine performance, make it a side mounted engine. I will leave it to you guys to figure out why.
03-30-2008 | 09:30 PM
#16
Senior Member
My Feedback: (3)
RE: Aerodynamic considerations for a speed plane design
A side mounted engine with rear exhaust really throws a wrench into the design of the airframe. I can't think of any dynamic reason why a rear exhaust engine would run any harder than side exhaust. A side mounted engine will see less fuel gravity change....is this what you are getting at?
So we are working with a side mounted, side exhaust engine, pipe-side-down?
So we are working with a side mounted, side exhaust engine, pipe-side-down?
03-30-2008 | 10:26 PM
#17
Thread Starter
RE: Aerodynamic considerations for a speed plane design
OK 15 cc/.96 or less ok that sounds like a good place to start.
Side mounted I have to think about, the first thing that springs to mind would be a lower exhaust exit under the belly.
Interesting place to start...
Side mounted I have to think about, the first thing that springs to mind would be a lower exhaust exit under the belly.
Interesting place to start...
03-30-2008 | 10:36 PM
#18
My Feedback: (1)
RE: Aerodynamic considerations for a speed plane design
Think about the polar moments of inertia. A vertically mounted engine is working against the polar moments of the fuselage while the side mounted is also working against the wing as well as the fuselage. With long wings of RC models, the effect is enhanced, so more of the energy works at turning the prop.
03-30-2008 | 10:46 PM
#19
Senior Member
My Feedback: (3)
RE: Aerodynamic considerations for a speed plane design
If the pipe tunnel is down below, it has to be made heavy enough to absorb landings. Plus think about the poor guy who has to launch the plane.
The pipe needs to be up, I think.
I still am not sold on the need for side mounting [for the purpose of maximizing engine output]. I don't think my Nelson cares which way it sits?.
High Plains has a lot of explaining to do.
I do think that a streamliner with a side mounted engine will be more work [>:]!
The pipe needs to be up, I think.
I still am not sold on the need for side mounting [for the purpose of maximizing engine output]. I don't think my Nelson cares which way it sits?.
High Plains has a lot of explaining to do.
I do think that a streamliner with a side mounted engine will be more work [>:]!
03-30-2008 | 10:47 PM
#20
Thread Starter
RE: Aerodynamic considerations for a speed plane design
Is the polar moment of inertia a quantity used to predict an object's ability to resist torsion, in objects (or segments of objects) with an invariant circular cross-section and no significant warping or out-of-plane deformation. Is it used to calculate the twist of an object subjected to a torque. And is analogous to the area moment of inertia, which characterizes an object's ability to resist bending and is required to calculate displacement?
I think I understand what you mean , so that the mass of the wings comes into play damping out the vibration of the motor and deformation of the fuselage?
I think I understand what you mean , so that the mass of the wings comes into play damping out the vibration of the motor and deformation of the fuselage?
03-30-2008 | 10:53 PM
#21
Thread Starter
RE: Aerodynamic considerations for a speed plane design
ORIGINAL: combatpigg
I do think that a streamliner with a side mounted engine will be more work [>:]!
I do think that a streamliner with a side mounted engine will be more work [>:]!
The prop would travel with less up and down distortion to its arc...
The lower exhaust was my first thought but I think this is a rear exhaust DF engine much like my OS 91 VF-df. Which means the exhaust would be straight back in the center of the fuselage, not a lower exhaust as I originally tossed out there.
03-30-2008 | 11:01 PM
#22
Senior Member
My Feedback: (3)
RE: Aerodynamic considerations for a speed plane design
My take.......the vertical moving piston is trying to lift and lower the plane in "pitch", but the sideways moving piston is trying to yaw the airframe against what is a better foundation, the long spanned wing. This would tend to smooth the engine out, too.
On a similar note, ever taken a running engine and grabbed the upper cylinder with a pair of channel locks? You might see a nice rpm jump, I know I have.
On a similar note, ever taken a running engine and grabbed the upper cylinder with a pair of channel locks? You might see a nice rpm jump, I know I have.
03-30-2008 | 11:07 PM
#23
Thread Starter
RE: Aerodynamic considerations for a speed plane design
I was just thinking about streamlining given the sidewinder mount, one cheek of the cowl is the cooling for the engine the other cheek houses the fuel tank. That would make for a symmetrical setup that could be blended into the fuselage side and wing root.
This is getting interesting!!!
This is getting interesting!!!
03-30-2008 | 11:09 PM
#24
My Feedback: (1)
RE: Aerodynamic considerations for a speed plane design
Engines always run best mounted to a couple hundred pounds of steel. But they usually don't fly too well hefting the weight. The next best thing is to use the dynamics of the models mass to create the stiffest possible engine mount. Take a wing in your hands and rotate it in the pitch axis, it takes next to no effort. Now rotate it in yaw, back and forth. Quite a difference!
